At least, they think they're cooking. Earlier studies have already shown that when taught by humans, bonobos, a close relative of chimps, can learn to cook their food. But now a new study indicates that the primates can develop the concept of cooking and the patience for delayed gratification all on their own.

The research was conducted by Alexandra Rosati, an evolutionary biologist at Yale, and Felix Warneken, a psychologist at Harvard University, at a chimpanzee sanctuary in the Democratic Republic of the Congo. The team didn't want to leave chimps to their own devices around real fire for fear that they would injure themselves, so instead they gave the animals a fake "oven" and some raw sweet potato. 

"You can think of it as a chimpanzee microwave where, basically, if the chimpanzees placed raw food in the device and then we shook the device, [the food] came out cooked," Rosati told NPR's The Salt.

What actually happened was that the researchers had already put pre-cooked food in a hidden compartment that opened when the device was shaken. But to the chimps, the effect was as if their raw food had been cooked. And over time, the chimps—who apparently prefer cooked sweet potatoes—learned to save their raw food for the chance to "cook" it.

"At first, the chimps pretty much ate the food. But then you almost could see them have this insight like, Oh, my goodness, I can put it in this device and it comes back cooked," Rosati said. And further experiments proved that chimps understood not just the shake-for-food aspect but also the "cooking" behind it. When given cooked sweet potato from the start, the chimps just ate the handout happily. But faced with a raw carrot, they showed self-restraint, holding on to the food until they had a chance to "cook" it.

Scientists are excited by this insight into how and when humans may have developed the ability to mix food and fire to develop cooking. Richard Wrangham, a professor of biological anthropology who has written on the subject said, "What we're seeing here is that the chimps are surprisingly similar to humans, even though the whole process of cooking seems like something that is a huge divide between humans and other animals."

[h/t The Salt]